The present invention generally relates to the field of microelectromechanical systems and, more particularly, to a microelectromechanical system that constrains the direction of forces acting on a load in a manner such that there is also a reduced potential for rubbing or contact between different portions of the system.
There are a number of microfabrication technologies that have been utilized for making microstructures (e.g., micromechanical devices, microelectromechanical devices) by what may be characterized as micromachining, including LIGA (Lithographie, Galvonoformung, Abformung), SLIGA (sacrificial LIGA), bulk micromachining, surface micromachining, micro electrodischarge machining (EDM), laser micromachining, 3-D stereolithography, and other techniques. Bulk micromachining has been utilized for making relatively simple micromechanical structures. Bulk micromachining generally entails cutting or machining a bulk substrate using an appropriate etchant (e.g., using liquid crystal-plane selective etchants; using deep reactive ion etching techniques). Another micromachining technique that allows for the formation of significantly more complex microstructures is surface micromachining. Surface micromachining generally entails depositing alternate layers of structural material and sacrificial material using an appropriate substrate which functions as the foundation for the resulting microstructure. Various patterning operations (collectively including masking, etching, and mask removal operations) may be executed on one or more of these layers before the next layer is deposited so as to define the desired microstructure(s). After the microstructure(s) has been defined in this general manner, the various sacrificial layers are removed by exposing the microstructure(s) and the various sacrificial layers to one or more etchants. This is commonly called xe2x80x9creleasingxe2x80x9d the microstructure(s) from the substrate, typically to allow at least some degree of relative movement between the microstructure(s) and the substrate. The etchant is biased to the sacrificial material to remove the same at a greater rate than the structural material. Preferably, the microstructure(s) is released without allowing the etchant to have an adverse impact on the structural material of the microstructure(s).
Microelectromechanical systems are typically actuated in a manner where the direction of the load forces are substantially collinear with the motion of the actuator. However, for some actuation systems, the load may be permitted to move in a path that is not collinear with the motion of the actuator (e.g., where the load moves out of plane). Off-axis forces (i.e., non-collinear) can result that can be detrimental to the operation of the actuator. For instance, actuator electrodes may short together or portions of the actuator may contact other surfaces of the microelectromechanical system, thereby adversely impacting the motion of the actuator. It would be desirable for the portion the load force that is transmitted to the actuator to be constrained to be at least substantially collinear with the motion of the actuator, thereby facilitating the proper operation of the actuator. In other words, it would be desirable for off-axis components of the load force to be isolated from the actuator by a force isolation system of sorts, or equivalently, by some way of constraining the direction of the force acting on the actuator. For most applications, and particularly for applications involving precise positioning of optical elements, it would be further desirable to provide this force isolation function in a manner that does not exhibit hysteretic behavior. This generally means that it would be desirable for none of the surfaces of such a force isolation system to come into contact or rub during normal operation of the microelectromechanical system.
A primary object of the present invention is to at least attempt to minimize off-axis forces of a load acting on a given microstructure, and do so in a way that does not produce rubbing or contacting surfaces. In one application of the present invention, the noted microstructure is an actuator. In this case, the present invention enables precise positioning of optical elements that involve out-of-plane motion, without exhibiting hysteretic behavior.
A first aspect of the present invention is embodied by a mirror positioning system that is fabricated using a substrate. The system includes a mirror that is interconnected with a portion of a first lever that is able to move relative to the substrate. The system further includes an actuator assembly that is interconnected with the substrate so as to be able to move relative thereto along a first path. A coupling assembly interconnects the actuator assembly with a portion of the first lever that is able to move relative to the substrate. Depending upon the direction that the actuator assembly moves along the first path, a first lever end either moves at least generally away from or toward the substrate, as will the portion of the mirror that is interconnected with the first lever. Movement of the actuator assembly and the resultant movement of the first lever end relative to the substrate exerts a force on the coupling assembly that is not collinear with the first path along with the actuator assembly moves. The mirror positioning system of the first aspect is configured to address this situation in at least two respects. One is that the mirror positioning system of the first aspect is configured to redirect the application of such a force to the actuator assembly so as to be at least generally collinear with the first path along which the actuator assembly moves relative to the substrate. Another is that the mirror positioning system of the first aspect is configured such that no portion of the coupling assembly is deflected by such a non-collinear force into contact with the substrate.
Various refinements exist of the features noted in relation to the subject first aspect of the present invention. Further features may also be incorporated in the subject first aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. The mirror may provide any appropriate optical function, including without limitation to reflect an optical signal, to change the direction of an optical signal, to change the focus of an optical signal, to attenuate an optical signal, to diffract an optical signal, or any combination thereof. The mirror may be interconnected with the substrate in any appropriate manner, including without limitation directly by pivotally interconnecting the mirror with the substrate utilizing one or more compliant members, indirectly via the first lever, or a combination thereof (e.g., by interconnecting one or more portions of the mirror with the substrate with one or more compliant members or flexures, and also by interconnecting one or more other portions of the mirror with the first lever). xe2x80x9cPivotally interconnectingxe2x80x9d or the like, as used herein, means any type of interconnection that allows a microstructure to at least generally undergo a pivoting or pivotal-like motion when exposed to an appropriate force, including without limitation any interconnection that allows a microstructure or a portion thereof to move at least generally about a certain axis. Representative pivotal interconnections include the use of a flexing or elastic deformation of a microstructure or a portion thereof, as well as the use of relative motion between two or more microstructures that are typically in interfacing relation during at least a portion of the relative movement (e.g., a hinge connection; a ball and socket connection).
The first lever may be interconnected with the substrate in any manner such that at least part of the first lever is able to move at least generally away from or toward the substrate. Whether at least part of the first lever moves at least generally away from or at least generally toward the substrate is dependent upon the direction of the resulting force that is acting on the first lever as noted above. Any way of interconnecting the first lever with the substrate that allows for the desired relative movement between the first lever and the substrate may be utilized. In addition, any configuration may be used for the first lever that allows for the desired relative movement between the first lever and the substrate (e.g., single or multiple beam structures of any appropriate configuration). The desired movement of the first lever relative to the substrate may be along any path (e.g., along an arcuate path) and in any orientation relative to the substrate (e.g., along a path that is normal to the substrate; along a path that is at an angle other than 90xc2x0 relative to the substrate).
The actuator assembly of the first aspect may include at least one actuator. That is, the actuator assembly may include a single actuator or multiple actuators that exert a concerted or collective force (directly or indirectly) on the first lever through the coupling assembly. If multiple actuators are used, the first path may be viewed as the cumulative path along which the actuators move. Any appropriate type of an actuator may be utilized in the case of the first aspect, including without limitation an electrostatic comb actuator, a thermal actuator, a piezoelectric actuator, a magnetic actuator, and an electromagnetic actuator. Control of the movement of any actuator assembly may be accomplished in any appropriate manner as well. In one embodiment, the signal that is used to control the movement of the actuator assembly originates external to a microelectromechanical system that may include the mirror positioning system of the first aspect. Both open loop and closed loop configurations may also be used for controlling the operation of the actuator assembly. Movement of the actuator assembly may be active (e.g., as a result of the application of or a change in an external signal thereto), passive (e.g., utilizing a stored spring force or the like), or a combination thereof.
The coupling assembly utilized by the first aspect may be of any relevant configuration, may include one or more microstructures, and broadly encompasses the entirety of the structural interconnection between the actuator assembly and the first lever. The coupling assembly may include a coupling or tether that is interconnected (directly or indirectly) with both the actuator assembly and the first lever. Any appropriate configuration may be used for any such tether. In at least certain applications, it may be desirable to have this tether be xe2x80x9cstiff.xe2x80x9d A xe2x80x9cstiff tetherxe2x80x9d means that such a tether is sufficiently stiff so as to not buckle, flex, or bow to any significant degree when exposed to external forces typically encountered during normal operation of the mirror positioning system. As such, no significant elastic energy is stored in the tether, the release of which could adversely affect one or more aspects of the operation of the mirror positioning system.
Other microstructures that may be included in the coupling assembly of the first aspect include a pivotless compliant microstructure that will be discussed in more detail below. In one embodiment, the coupling assembly microstructure includes both a pivotless compliant microstructure and a tether of the above-described. The actuator assembly may be appropriately interconnected with an input section of the pivotless compliant microstructure, the tether may extend between and interconnect an output section of the pivotless compliant microstructure with the first lever, and the mirror is appropriately interconnected with a portion of the first lever that is able to move at least generally away from or toward the substrate, depending on the direction of motion of the actuator assembly.
One way in which the force redirection function associated with the first aspect may be addressed (the xe2x80x9cfirst conditionxe2x80x9d) at least in part is through the use of one or more doubly clamped beams. One or more doubly clamped beams or the like may be attached to one or more appropriate portions of the coupling assembly to limit the amount of vertical movement of the same relative to the substrate when exposed to a vertical force component, which in turn reduces the magnitude of the vertical force component that is ultimately transmitted to the actuator assembly. Doubly clamped beams are microstructures that are anchored to the substrate at least at one location on each side of the portion of the coupling assembly to which the given doubly clamped beam is anchored or attached.
An appropriately configured pivotless compliant microstructure may be incorporated into the coupling assembly in the case of the first aspect to at least assist in the provision of the force redirection function (the xe2x80x9cfirst conditionxe2x80x9d). A pivotless compliant microstructure, as used herein, means a microstructure having: 1) a plurality of flexible beams that are each attached or anchored (directly or indirectly) to the substrate at a discrete location so as to be motionless relative to the substrate at the attachment or anchor location, and such that other portions of each such flexible beam are able to move relative to the substrate by a flexing or bending-like action; 2) a plurality of cross beams that are not attached to the substrate (other than through an interconnection with one or more flexible beams), and that either interconnect a pair of flexible beams at a location that is able to move relative to the substrate or that interconnect with one or more other cross beams; 3) an appropriate input structure (e.g., a single beam; a yoke) and an appropriate output structure (e.g., a single beam; a yoke); and 4) of a configuration that exploits elastic deformation to achieve a desired movement of the input structure and the output structure relative to the substrate. Stated another way, all movement the pivotless compliant microstructure is through a flexing of the same at/about one or more locations where the structure is anchored to the substrate. This pivotless compliant microstructure may be configured to achieve any type/amount of motion of its input structure relative to its output structure. For instance, the input and output structures may move the same or different amounts in the lateral dimension (at least generally parallel with the plane of the substrate). In the case where the output structure of the pivotless compliant microstructure moves more than its input structure, the pivotless compliant microstructure may be referred to as a displacement multiplier. Therefore, a displacement multiplier is one type of pivotless compliant microstructure which may be utilized in relation to the first aspect.
Further features may be incorporated into the above-noted pivotless compliant microstructure in the case of the first aspect to enhance the manner in which a force from the movement of the first lever end relative to the substrate is transmitted to actuator assembly so as to be collinear with the direction in which the actuator assembly moves relative to the substrate (the xe2x80x9cfirst conditionxe2x80x9d), to reduce the potential for contact with the underlying substrate (the xe2x80x9csecond conditionxe2x80x9d), or a combination thereof. For instance, the pivotless compliant microstructure may utilize a relief structure as its output structure and that is attached to a tether of the above-noted type, that in turn is attached to the first lever. This relief structure may be configured to reduce the amount that other portions of the pivotless compliant microstructure deflect toward the underlying substrate when non-collinear forces are exerted on the relief structure and the input structure. Both the bending stiffness of this relief structure, how/where the relief structure is attached to the remainder of the pivotless compliant microstructure, or both may be selected such that the torque that is exerted on the remainder of the pivotless compliant microstructure by the first lever/mirror reduces the potential for deflecting any portion of the pivotless compliant microstructure toward the substrate in an amount so as to contact any underlying structure during normal operation of the mirror positioning system of the first aspect.
Other options may be utilized to address reducing the potential for undesired contact between portions of the microelectromechanical system of the first aspect when using a pivotless compliant microstructure as at least part of the coupling assembly. For instance, the pivotless compliant microstructure may be allowed to move at least generally away from the substrate so as to increase the spacing from the underlying structure and including the substrate. The pivotless compliant microstructure may be mounted on a frame (typically at four anchor locations, although any appropriate number of anchor locations may be utilized), that in turn is pivotally interconnected with the substrate or that is interconnected with the substrate so as to allow at least part of the frame to be able to move at least generally away from the substrate. This frame may be configured as a one-piece structure or by a plurality of individual frame segments that are each interconnected with the substrate in the above-noted manner and that collectively define the frame. Moreover, this frame may be configured so as to be rigid or so as to not flex to a significant degree, or at least may be configured so as to be more rigid than the pivotless compliant microstructure that is mounted thereon. In this case the pivotless compliant microstructure would move at least generally away from the substrate (or further from the substrate) when exposed to non-collinear forces at its input and output structures by a pivoting of the xe2x80x9cfree endxe2x80x9d of the frame at least generally away from the substrate. Another option is for the frame to be defined by one or more pre-stressed elevators. A xe2x80x9cpre-stressed elevatorxe2x80x9d is a structure that may be made by surface micromachining, and that when released (after being exposed to one or more release etchants to remove a sacrificial material used in the fabrication of the mirror positioning system of the first aspect, and likely further after having one or more retention pins, fuses, or the like blown or ruptured (a retention pin, fuse, or the like being used to retain the prestressed elevators in a predetermined position relative to the substrate until operation of the mirror positioning system is initiated)) has at least a portion thereof change its position relative to the substrate. For instance, such a pre-stressed elevator may be anchored to the substrate during fabrication such that when released in the above-noted manner, at least one end of the pre-stressed elevator moves at least generally away from the substrate as a result of the energy stored therein during fabrication. Stated another way, a pre-stressed elevator may have a bent or curled configuration in the static state. Mounting the pivotless compliant microstructure on a portion of one or more of these pre-stressed elevators thereby increases the spacing between the pivotless compliant microstructure and the substrate, even prior to exposing its input and output structures to non-collinear forces. Yet another option is to pivotally interconnect the pivotless compliant microstructure itself with the substrate so as to allow part of the pivotless compliant microstructure to move at least generally away from the substrate when exposed to non-collinear forces. In one embodiment, this pivotal interconnection of the pivotless compliant microstructure is provided by limiting the anchor locations of the pivotless compliant microstructure to the substrate to being at least generally disposed along a common reference axis (e.g., anchoring the pivotless compliant microstructure at a pair of locations, which at least generally define a pivot axis).
Another option for reducing the potential for contact as a result of non-collinear forces being exerted on the input and output structure of a pivotless compliant microstructure is by forming a cavity under at least a portion of the pivotless compliant microstructure (or stated another way to increase the distance between at least a certain portion of the pivotless compliant microstructure and any underlying structure). Discrete cavities may be formed in the substrate under those portions of the pivotless compliant microstructure that are susceptible to being deflected the furthest in the direction of the substrate when exposed to non-collinear forces at its input and output structures. In this case, the spacing between those portions of the pivotless compliant microstructure that are susceptible to the most deflection could be spaced further from the underlying substrate than other portions of the pivotless compliant microstructure in the static state. Yet another option is to dispose the entire pivotless compliant microstructure in a cavity that is formed in the substrate. A related option would be to dispose at least a substantial portion of the pivotless compliant microstructure and its anchors to the substrate within a single cavity that is formed in the substrate. For instance, a single cavity could be formed in the substrate and all free ends or nodes of the pivotless compliant microstructure could be disposed in this single cavity. xe2x80x9cFree endsxe2x80x9d or xe2x80x9cnodesxe2x80x9d in this sense are those portions of the pivotless compliant microstructure that in effect are the extreme end of a cantilever or the like. Although the anchors between the pivotless compliant microstructure and the substrate may be disposed within a single cavity, in one embodiment all of the anchors between the pivotless compliant microstructure and the substrate are disposed outside of this cavity, while the remainder of the pivotless compliant microstructure is disposed within this single cavity.
Controlling the spacing between at least certain portions of the pivotless compliant microstructure and the underlying substrate may be used to address the second condition in relation to the first aspect as noted. In one embodiment, at least a portion of the pivotless compliant microstructure and the underlying substrate are separated by a space of at least about 7 microns. More preferably, each of the above-noted xe2x80x9cfree endsxe2x80x9d or xe2x80x9cnodesxe2x80x9d of the pivotless compliant microstructure are separated from the underlying substrate by the above-noted spacing. One way in which this may be achieved for the mirror positioning system of the first aspect when fabricated by surface micromachining techniques is to form the various beams of the pivotless compliant microstructure from only two of the structural layer levels in this system.
Selecting the locations where the pivotless compliant microstructure is anchored to the substrate may also address the potential for undesired contact between different portions of the mirror positioning system of the first aspect due to the existence of non-collinear forces being exerted on the coupling assembly. The pivotless compliant microstructure may be characterized as having a longitudinal extent progressing from its input structure to its output structure along a central, longitudinal reference axis. A pair of xe2x80x9clateralxe2x80x9d extremes of the pivotless compliant microstructure are disposed on opposite sides of this central, longitudinal reference axis and correspond with those portions of the pivotless compliant microstructure that are disposed furthest from this central, longitudinal reference axis. All anchor locations of the pivotless compliant microstructure to the substrate may be disposed at least as far from the output structure of the pivotless compliant microstructure (measured along the central, longitudinal reference axis or a parallel axis) as these lateral extremes to address the second condition of the first aspect. Stated another way, all anchor locations of the pivotless compliant microstructure to the substrate are disposed no farther from the input structure of the pivotless compliant microstructure than the noted lateral extremes, again measured along the central, longitudinal reference axis or a parallel axis.
A second aspect of the present invention is embodied in a microelectromechanical system that includes a substrate and a pivotless compliant microstructure of the type discussed above in relation to the first aspect. An appropriate load is interconnected with both the input and output structures of the pivotless compliant microstructure. For instance, an actuator assembly of the type discussed above in relation to the first aspect may be interconnected with the input structure, while a tether of the type discussed above in relation to the first aspect may be interconnected with the output structure of the pivotless compliant microstructure. Regardless of the actual loads that are interconnected with the input and output structures, the pivotless compliant microstructure of the second aspect utilizes a relief structure at its output structure. This relief structure is configured to reduce the amount that other portions of the pivotless compliant microstructure deflect toward the underlying substrate when non-collinear forces are exerted on the relief structure and the: input structure. Both the bending stiffness of this relief structure, how/where the relief structure is attached to the remainder of the pivotless compliant microstructure, or both may be selected such that the torque that is exerted on the remainder of the pivotless compliant microstructure by the first lever/mirror reduces the potential for deflecting any portion of the pivotless compliant microstructure toward the substrate in an amount so as to contact an underlying structure during normal operation of the microelectromechanical system.
A third aspect of the present invention is embodied in a microelectromechanical system that includes a substrate and a pivotless compliant microstructure of the type discussed above in relation to the first aspect. An appropriate load is interconnected with both the input and output structures of the pivotless compliant microstructure. For instance, an actuator assembly of the type discussed above in relation to the first aspect may be interconnected with the input structure, while a tether of the type discussed above in relation to the first aspect may be interconnected with the output structure of the pivotless compliant microstructure. Regardless of the actual loads that are interconnected with the input and output structures, a plurality of interconnected beams of the pivotless compliant microstructure are disposed between its input and output structures, and pivot relative to the substrate and/or other beams of the pivotless compliant microstructure to provide a desired lateral displacement between the input and output structures. At least two beams of the pivotless compliant microstructure extend at least generally away from each other at a first longitudinal location (relative to the central, longitudinal reference axis of the pivotless compliant microstructure). The input structure of the pivotless compliant microstructure is disposed at a second longitudinal location (relative to the noted central, longitudinal reference axis) that is spaced from this first longitudinal location. Where an appropriate load attaches to the output structure of the pivotless compliant microstructure is disposed at a third longitudinal location (relative to the noted central, longitudinal reference axis) that is between the first and second longitudinal locations.
A fourth aspect of the present invention is embodied in a microelectromechanical system that includes a substrate and a pivotless compliant microstructure of the type discussed above in relation to the first aspect. An appropriate load is interconnected with both the input and output structures of the pivotless compliant microstructure. For instance, an actuator assembly of the type discussed above in relation to the first aspect may be interconnected with the input structure, while a tether of the type discussed above in relation to the first aspect may be interconnected with the output structure of the pivotless compliant microstructure. Regardless of the actual loads that are interconnected with the input and output structures, the pivotless compliant microstructure is interconnected with the substrate so that its output structure is able to move at least generally away from the substrate so as to increase the spacing from the underlying structure.
Various refinements exist of the features noted in relation to the subject fourth aspect of the present invention. Further features may also be incorporated in the subject fourth aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. Any number of options may be employed to realize the above-noted type of movement pivotless compliant microstructure. The pivotless compliant microstructure may be mounted on a frame (typically at four anchor locations, although any appropriate number of anchor locations may be utilized), that in turn is pivotally interconnected with the substrate or that is interconnected with the substrate so as to allow at least part of the frame to be able to move at least generally away from the substrate. This frame may be configured as a one-piece structure or by a plurality of individual frame segments that are each interconnected with the substrate in the above-noted manner and that collectively define the frame. Moreover, this frame may be configured so as to be rigid or so as to not flex to a significant degree, or at least may be configured so as to be more rigid than the pivotless compliant microstructure that is mounted thereon. In this case the pivotless compliant microstructure would move at least generally away from the substrate (or further from the substrate) when exposed to non-collinear forces at its input and output structures by a pivoting of the xe2x80x9cfree endxe2x80x9d of the frame at least generally away from the substrate.
Another option is for the above-noted frame for the fourth aspect to be defined by on one or more pre-stressed elevators. A xe2x80x9cpre-stressed elevatorxe2x80x9d is a structure that may be made by surface micromachining, and that when released (after being exposed to one or more release etchants to remove a sacrificial material used in the fabrication of the microelectromechanical system of the first aspect, and likely further after having one or more retention pins, fuses, or the like blown or ruptured (a retention pin, fuse, or the like being used to retain the prestressed elevators in a predetermined position relative to the substrate until operation of the mirror positioning system is initiated)) has at least a portion thereof change its position relative to the substrate. For instance, such a pre-stressed elevator may be anchored to the substrate during fabrication such that when released in the above-noted manner, at least one end of the prestressed elevator moves at least generally away from the substrate as a result of the energy stored therein during fabrication. Stated another way, a pre-stressed elevator may have a bent or curled configuration in the static state. Mounting the pivotless compliant microstructure on a portion of one or more of these pre-stressed elevators thereby increases the spacing between the pivotless compliant microstructure and the substrate, even prior to exposing its input and output structures to non-collinear forces.
Yet another option that may be employed in relation to the fourth aspect is to pivotally interconnect the pivotless compliant microstructure itself with the substrate so as to allow part of the pivotless compliant microstructure to move at least generally away from the substrate when exposed to non-collinear forces. In one embodiment, this pivotal interconnection of the pivotless compliant microstructure is provided by limiting the anchor locations of the pivotless compliant microstructure to the substrate to being at least generally disposed along a common reference axis. In another embodiment, the pivotless compliant microstructure is interconnected with the substrate at only two locations.
A fifth aspect of the present invention is embodied in a microelectromechanical system that includes a substrate and a pivotless compliant microstructure of the type discussed above in relation to the first aspect. An appropriate load is interconnected with both the input and output structures of the pivotless compliant microstructure. For instance, an actuator assembly of the type discussed above in relation to the first aspect may be interconnected with the input structure, while a tether of the type discussed above in relation to the first aspect may be interconnected with the output structure of the pivotless compliant microstructure. Regardless of the actual loads that are interconnected with the input and output structures, a cavity is formed under at least a portion of the pivotless compliant microstructure (or stated another way to increase the distance between at least a certain portion of the pivotless compliant microstructure and the substrate).
Various refinements exist of the features noted in relation to the subject fifth aspect of the present invention. Further features may also be incorporated in the subject fifth aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. Discrete cavities may be formed in the substrate under those portions of the pivotless compliant microstructure that are susceptible to being deflected the furthest in the direction of the substrate when exposed to non-collinear forces. In this case, the spacing between those portions of the pivotless compliant microstructure that are susceptible to the most deflection could be spaced further from the underlying substrate than other portions of the pivotless compliant microstructure in the static state. Yet another option is to dispose the entire pivotless compliant microstructure in a cavity that is formed in the substrate. A related option would be to dispose at least a substantial portion of the pivotless compliant microstructure and its anchors to the substrate within a single cavity that is formed in the substrate. For instance, a single cavity could be formed in the substrate and all free ends or nodes of the pivotless compliant microstructure could be disposed in this single cavity. xe2x80x9cFree endsxe2x80x9d or xe2x80x9cnodesxe2x80x9d in this sense are those portions of the pivotless compliant microstructure that in effect are the extreme end of a cantilever or the like. Although the anchors between the pivotless compliant microstructure and the substrate may be disposed within a single cavity, in one embodiment all of the anchors between the pivotless compliant microstructure and the substrate are disposed outside of this cavity, while the remainder of the pivotless compliant microstructure is disposed within this single cavity.
A sixth aspect of the present invention is embodied in a microelectromechanical system that includes a substrate and a pivotless compliant microstructure of the type discussed above in relation to the first aspect. An appropriate load is interconnected with both the input and output structures of the pivotless compliant microstructure. For instance, an actuator assembly of the type discussed above in relation to the first aspect may be interconnected with the input structure, while a tether of the type discussed above in relation to the first aspect may be interconnected with the output structure of the pivotless compliant microstructure. Regardless of the actual loads that are interconnected with the input and output structures, the pivotless compliant microstructure may be characterized as having a longitudinal extent progressing from its input structure to its output structure along a central, longitudinal reference axis. A pair of xe2x80x9clateralxe2x80x9d extremes of the pivotless compliant microstructure are disposed on opposite sides of this central, longitudinal reference axis and correspond with those portions of the pivotless compliant microstructure that are disposed furthest from this central, longitudinal reference axis. All anchor locations of the pivotless compliant microstructure to the substrate may be disposed at least as far from the output structure of the pivotless compliant microstructure (measured along the central, longitudinal reference axis or a parallel axis) as these lateral extremes to address the second condition of the first aspect. Stated another way, all anchor locations of the pivotless compliant microstructure to the substrate are disposed no farther from the input structure of the pivotless compliant microstructure than the noted lateral extremes, again measured along the central, longitudinal reference axis or a parallel axis.
A seventh aspect is embodied by a microelectromechanical system that includes first and second loads that are interconnected by a coupling assembly. The first and second loads exert non-collinear forces on the coupling assembly. At least one doubly clamped beam is attached to at least one part of the coupling assembly to address the existence of these non-collinear forces. One or more doubly clamped beams or the like may be attached to one or more appropriate portions of the coupling assembly to limit the amount of vertical movement of the same relative to the substrate when exposed to a vertical force component, which in turn reduces the magnitude of the vertical force component that is ultimately transmitted to the actuator assembly. Doubly clamped beams are microstructures that are anchored to the substrate at least at one location on each side of the portion of the coupling assembly to which the given doubly clamped beam is anchored or attached.
The various aspects of the present invention may be used alone or in any desired combination. In one embodiment, the first aspect utilizes the features discussed in relation to the second aspect and the fifth aspects. Moreover, each of the second through the eighth aspects may be used in a mirror positioning system that includes a mirror, a first lever, an actuator assembly, and a coupling assembly of the type discussed above in relation to the first aspect.